Organic el light-emitting element and manufacturing method thereof

ABSTRACT

An organic EL light-emitting element is provided in which, by means of an organic material that is oligomeric, an organic layer coated film 25 is formed in a high-definition pixel pattern in the openings 23a of insulation banks 23 that are formed to be hydrophilic; a manufacturing method of said organic EL light-emitting element is also provided. The coated film 25 is formed by dropwise injection of a liquid composition containing an organic material oligomer.

TECHNICAL FIELD

The present disclosure relates to an organic EL light-emitting element(organic electroluminescent light-emitting element) and a method ofmanufacturing the same.

BACKGROUND ART

An organic EL light-emitting element is formed such that a thin layer oforganic material containing an organic light-emitting substance issandwiched between an anode and a cathode. This organic thin layer isformed by a vapor deposition method or a coating method. In a method ofmanufacturing of a vapor-deposition type organic thin layer, asupporting substrate (a substrate to be vapor-deposited) and adeposition mask are arranged overlapped, an organic material isvapor-deposited in vacuum through an opening of the deposition mask, anda thin layer is formed on the supporting substrate. In general, lowmolecular weight compounds are used as an organic material for avapor-deposition type organic material. On the other hand, in a methodof manufacturing of a coated-type organic EL light-emitting element, athin layer is formed on a supporting substrate using a solution for, forexample, a printing process such as a screen printing, an ink-jetprocess. An organic EL light-emitting element which is produced by acoating process can be produced at a lower manufacturing cost comparedto an organic EL light-emitting element which is produced by avapor-deposition process since, for example, it does not require anexpensive vapor mask or equipment for high vacuum process, and anefficiency in use of an organic material in a coating process is higherthan a vapor-deposition process. However, it is difficult to produce agood quality thin layer using a coating process since low molecularweight compounds tend to be easily crystalized. Therefore, polymercompounds having a high amorphous property have been used as an organicmaterial in the coating process. For example, Patent Document 1describes a polymer compound containing a specific repeating unit as anorganic material for a coated-type organic EL light-emitting element,which can be used as a light-emitting material or charge transportmaterial. A polymer compound used in a coating process usually containsat least a number of several tens or more of such repeating units.

PRIOR ART DOCUMENT Patent Document Patent Document 1: JP 2011-223015 ASUMMARY OF THE INVENTION Problems to be Solved by the Invention

As mentioned above, a polymer compound is used for an organic materialfor a coated-type organic EL light-emitting element. However, in theconventional coated-type organic EL light-emitting element, it isdifficult to coat an organic material in a minute dot pattern since asize of a droplet of the organic material is hardly reduced even usingan ink-jet method. An attempt has been made to have a coating solutionwithin a pixel by devising an insulation bank arrangement when thedisplay apparatus is large-sized and the pattern formation has largearea, for example, a size of each pixel for the display apparatus is along-side length of 210 μm or more and a short-side length of 70 μm ormore.

However, an area for each pixel of the display apparatus becomes verysmall with the reduced weight, size, and thickness and the highdefinition of the recent electronic apparatus such as a portable device,making unable to separately coat on each pixel even using an ink-jetmethod, since the droplet spreads across more than one pixels. Also, thepurification of polymer compounds is difficult, and it is hard to obtainhighly purified polymer compounds. Therefore, when the polymer compoundsare used for an organic EL light-emitting element, a luminescent colorpurity, a light emission efficiency, a brightness and so on might bereduced. Further, if the molecular weight of the polymer compoundbecomes too high, forming a homogeneous layer may become difficult dueto a gelation of polymer compounds.

Further, it has been generally known that the light emission efficiencyof the low molecule weight compounds is greater than that of the polymercompounds, the life of the low molecule compounds is longer than that ofthe polymer compounds, variations in color realized with the lowmolecule weight compounds is greater than that realized with the polymercompounds, and the performance in blue light emission of the lowmolecule weight compounds is especially superior compared to that of thepolymer compounds. However, a coating solution containing a low moleculeweight compound has a high fluidity, thereby the coating solutionspreads right after being ejected from a discharge nozzle of the ink-jetapparatus, making it difficult to form a liquid drop of good quality,and, since the low molecule weight compounds tend to be easilycrystalized as described above, a layer of a low molecule material isformed in such a way that the material is inhomogeneously distributed,and thus it is difficult to use low molecule weight compounds for aconventional method of manufacturing a coated-type organic ELlight-emitting element.

As described above, when the polymer compounds are used for an organicmaterial, it is difficult to prepare a small liquid drop. Therefore,when a pixel size becomes small, a problem arises that a separatecoating with high definition on an electrode of the small pixel isunable to be carried out even using an ink-jet method. Further, thedifficulty has been enhanced in selectively coating a small-sizeddesired area with the organic material, depending on a droplet diameterof a liquid drop to be ejected, while a technique for manufacturing anorganic layer with smaller size and higher definition for, for example,display apparatus for a smartphone is demanded. The inventors have foundthat a small-sized liquid droplet can be obtained by using a coatingsolution containing an oligomer of an organic material and a preciseseparate coating of even a small area can be carried out.

The present invention has been made based on such circumstances asmentioned above, and an object of the present invention is to provide anorganic EL light-emitting element having an organic layer with a smallsize and a high definition pattern without making a surface of aninsulation bank liquid repellent and without forming an insulation bankin a reversed tapered shape, by using an inexpensive printing method forthe organic layer formation, and a manufacturing method thereof.

Means to Solve the Problem

An organic EL light-emitting element according to the first embodimentof the present application comprises a substrate, a first electrodeprovided on a surface of the substrate, an insulation bank formed tosurround at least part of the first electrode, an organic layer formedon the first electrode surrounded by the insulation bank, and a secondelectrode formed on the organic layer, wherein the insulation bank has aforward tapered shape or a sidewall of the insulation bank is formedsuch as to be substantially perpendicular to the first electrode, and asurface of the insulation bank is formed to have a hydrophilic property,and the organic layer is a coated-type organic layer comprising anoligomer of an organic material.

A method of manufacturing an organic EL light-emitting element accordingto the second embodiment of the present application comprises forming afirst electrode on a surface of a substrate, forming an insulation bankto surround at least part of the first electrode, forming a coated-typeorganic layer on an area of the first electrode surrounded by theinsulation bank, and forming a second electrode on the organic layer,wherein the method comprises conducting a modifying treatment toincrease a hydrophilicity to a surface of a sidewall of an openingsurrounded by the insulation bank before forming the organic layer, anda step for forming the organic layer is conducted by applying a dropletof a liquid composition comprising an oligomer of an organic materialusing an ink-jet process.

Effect of the Invention

According to the first embodiment of the present application, an organicEL light-emitting element is formed with a coated-type organic layercontaining an oligomer of an organic material, thereby it is notnecessary to subject an insulation bank to a liquid repellent treatment.Thus, a deterioration of the organic layer by fluorine which iscontained in a material for a liquid repellent property or introduced ina material by a surface treatment does not occur. Further, since thereis no need to form an insulation bank in a reversed tapered shape,manufacturing can be facilitated and an occurrence of a stepwisedisconnection of a second electrode can be prevented. A coated-typeorganic EL light-emitting element is provided in which each pixel of adisplay apparatus can be constituted by a separate coating of even avery small light-emitting area with a size of, for example, 10 μm squareto 50 μm square. Further, according to the second embodiment of thepresent application, since a coating solution containing an oligomer ofan organic material is used and thus a small-sized liquid droplet isejected and dropped using an ink-jet process, an organic ELlight-emitting element in which a coated-type organic layer is formed ina high definition pattern can be provided. Therefore, a precise coatingof a small area can be conducted without making a surface of aninsulation bank liquid repellent, and a coating solution can be coateduniformly inside an opening. Consequently, a small, high-definitionorganic EL light-emitting element can be obtained at a low cost and asmall, high-definition display apparatus can be manufacturedinexpensively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a coating process in a method of manufacturing an organicEL light-emitting element according to one embodiment of the presentapplication.

FIG. 1B shows a state in which a coated layer containing an oligomer ofan organic material is formed on an electrode during a manufacturingprocess.

FIG. 1C shows a cross-sectional view of an organic EL light-emittingelement according to one embodiment of the present application.

FIG. 2 shows a flowchart of a manufacturing process according to oneembodiment of the present application.

EMBODIMENT FOR CARRYING OUT THE INVENTION

The invention will be further described below. The embodiments describedbelow are intended only to provide an example of the disclosure and theinvention is not limited to certain embodiments described below.

As illustrated in FIG. 1C, which shows a schematic cross-sectional viewof an organic EL light-emitting element, an organic EL light-emittingelement according to the presently illustrated embodiment comprises asubstrate 21, a first electrode 22 (an anode, for example) provided on asurface of the substrate 21, an insulation bank 23 formed to surround atleast part of the first electrode 22, an organic layer 26 formed on thefirst electrode 22 surrounded by the insulation bank 23, a secondelectrode 27 formed on the organic layer 26, and a protection layer 28formed on the second electrode 27. The insulation bank 23 has a forwardtapered shape or a sidewall of the insulation bank 23 is formed such asto be substantially perpendicular to the first electrode 22, a surfaceof the insulation bank 23 is formed to have a hydrophilic property, andthe organic layer 26 is formed by a coated-type organic layer containingan oligomer of an organic material.

The term “coated-type organic layer” is used herein to refer to theorganic layer prepared by drying a coated layer formed by coatingprocess, for example, a coated layer of an organic material formed usinga dispenser and a coated layer formed by a printing process such as ascreen printing or an ejection of organic material drops by ink-jetprocess. When a shape of a sidewall of the insulation bank 23, whichforms an opening, is formed such that a spacing between sidewalls of theinsulation bank 23 in a vertical cross sectional view is increased froma surface of the first electrode 22 toward a top surface of theinsulation bank 23, the shape of the insulation bank 23 is referred toherein as “forward tapered shape”. The term “formed to have ahydrophilic property” is used herein to refer to not only what is formedby specifically being subjected to a hydrophilic treatment but also whathas no liquid repellent property obtainable by using a material with aliquid repellent property or through a liquid repellent treatment.

As described above, the conventional, coated-type organic ELlight-emitting element has a problem in that the element cannot beformed in a small-sized light-emitting area. When coating an organicmaterial on an area of the electrode, which will constitute each pixel,by, for example, ink-jet process for manufacturing a display apparatus,it is necessary to adjust a physical property of a coating solutionejected from a nozzle of ink-jet apparatus and optimize a ejecting speedof a liquid drop of a coating solution when ejected and a printingcondition of an ink-jet apparatus, however, the inventors have found outthat among those a size of a liquid drop of a coating solution whenbeing ejected is an important factor to determine a possible size of anarea to which an organic layer is provided, and that it is veryimportant to adjust a size of a liquid drop to a desirable size at apattern forming using an ink-jet process. With a conventional coatingsolution, a volume of a liquid drop when a coating solution of anorganic material being ejected using an ink-jet process is about 5 pL to30 pL in average, and it is impossible to reduce the volume of a coatingsolution per one drop to 1 pL or less. However, as a result of theinventors' extensive studies, the inventors found out that the reasonwhy a size of the conventional liquid drop cannot be reduced isattributed to a polymer with a high molecular weight. The inventorsfound out that a droplet of 0.05 to 1 pL can be obtained by using anoligomer having a molecular weight of 5000 or less.

As a result of further extensive studies of inventors, the inventorsfound out that a size of a liquid drop is largely affected by amolecular weight of an organic material. In other words, the inventorsascertain that the reason why small droplets cannot be formed isattributed to a fact that a solute (an organic material) in theconventional coating solution is a polymer compound having a high degreeof polymerization and a large molecular weight of 10000 or more. It isconsidered that a size of a liquid drop is affected by a concentrationof an organic material in a coating solution (a solubility of an organicmaterial in a solvent) or a viscosity of a coating solution, however,the inventors conducted a test under the condition in which aconcentration is as high as possible, yet a dropping of the solution isenable to be conducted.

As a result, the inventors found out that when a molecular weight is 300or more and 5000 or less, preferably about 3000 or less, more preferably500 or more and 1000 or less, a liquid droplet volume per one drop canbe set to about 0.05 pL to about 1 pL. The inventors conducted variousstudies with different polymerization methods and tested variouscompounds with a smaller molecular weight, i.e. a smaller degree ofpolymerization, and, as a result, the inventors found out that a liquiddrop with the above-mentioned size can be obtained by using an organicmaterial having a certain polymerization degree, which can form anoligomer (generally around or less than an icosamer), preferably andimer to decamer.

As described above, for the conventional, coated-type organic ELlight-emitting element, a size of a light-emitting area of the organicEL light emitting element cannot be reduced to 70 μm×70 μm or less. Thismeans that when a length of one side of a light-emitting area is 70 μmor less, a liquid drop will overflow from the area. Therefore, a pixelsize corresponding to a 20-inch QHD display, which is, a size of 70μm×210 μm, is a limit size of the area that can be formed in theconventional, coated-type organic EL light-emitting element. Even withthis size of light-emitting area, various improvements to an insulationbank were needed, as described above. Those improvements are describedbelow. The exemplary organic EL light-emitting element according to thepresent application will be described in the followings by referring toFIGS. 1A to 1C, in which an insulation bank 23 is formed in a peripheryof a first electrode 22, and an organic layer 26 is coated on the firstelectrode 22 in an opening 23 a surrounded by the insulation bank 23.This organic layer 26 forming area constitutes a light-emitting area.When a plurality of organic EL light-emitting elements are arranged inmatrix form on the organic layer 26 to form a display apparatus, asecond electrode 27 (see FIG. 1C) may be formed across the entiresurface continuously.

In the conventional, coated-type organic EL light-emitting elementhaving such a structure, when the organic EL light-emitting elements arearranged in matrix form in a display apparatus, a coating solutionoverflows an opening 23 a surrounded by the insulation bank 23 andspreads to neighboring light-emitting s area since a liquid dropletvolume per one drop ejected by an ink-jet process is large, as describedabove. To avoid this problem, the surface of a sidewall of the opening23 a surrounded by the insulation bank 23 and the top surface of theinsulation bank 23 are formed to have a liquid repellent property. Withsuch a liquid repellent treatment, a dripped coating solution is likelyrepelled by the insulation bank 23 even when the volume of the drippedcoating solution is larger than a volume within the opening 23 a, andthe coating solution is pulled into a spherical shape due to a surfacetension of the coating solution, raised in the vertical direction andkept in an opening 23 a, without overflowing the insulation bank 23 andspreading to areas of neighboring light-emitting elements from a smalllight-emitting area. To obtain such a liquid repelling property, aninsulation bank 23 is need to be either formed by a fluorine resincontaining fluorine, such as a polyamide containing fluorine, or asilicone resin, or subjected to a plasma treatment for treating asurface of the insulation bank 23 by, for example, CF₄ based gas, bothof which can be a difficult work and may increase a manufacturing cost.There is also a possibility that an effusion of fluorine to an organiclayer or an exposure to the fluorine gas may have an adverse effect.Further, it seems difficult to completely prevent the wetting spread ofthe coating solution to the neighboring light-emitting areas.

Further, as for other attempts for the improvement of the coated-typeorganic EL light-emitting element, an attempt to increase a height h1 ofan insulation bank 23 from a first electrode 22 (see FIG. 1A,hereinafter simply referred to as “a height of an insulation bank 23”)has been made. In this attempt, an insulation bank 23 is formed so as tohave a height h1 of 2 μm or more, resulting in an increment of a volumewithin an opening 23 a, and thus, a rather large liquid drop can be keptin an opening 23 a. However, when a height h1 of an insulation bank 23is increased, a height difference between a surface of an organic layer26 and a top surface of the insulation bank 23 will become large. Thisleads a problem in that a second electrode 27 which is formed across anentire surface of an organic layer 26 and top surface of the insulationbank 23 is likely disconnected stepwisely. To prevent this stepwisedisconnection problem, it is necessary to form a second electrode 27 tohave a thickness of 1 μm or more. This causes problems in that a timerequired for forming a second electrode 27 will become longer, and thatmore material will be needed for forming a second electrode 27, whichresults in an increment in the cost, and in addition to these problems,light can hardly be transmitted through such an electrode. As a result,this causes a problem in that an organic EL light-emitting element of atop emission type, in which light is taken out from a top surface, i.e.from a surface including the second electrode 27, cannot be produced.Further, when the height of the insulation bank is increased, lightemissions in oblique directions may be blocked, resulting in poorviewing angle characteristics. Further, in order to form an insulationbank with a high height, it is necessary to form an insulation bank insuch a way to have a large width. This demands a wide pixel pitch,causing the problem in that a high definition pattern is hard to beobtained.

Further, as for other attempts, an attempt to prevent a coating solutionfrom spreading over a neighboring light-emitting area has been made byforming an insulation bank 23 in a way to have a reversed tapered shape(the shape in which a spacing between sidewalls of the insulation bank23 in a vertical cross sectional view is decreased from a surface of thefirst electrode 22 toward a top surface of the insulation bank 23, i.e.a reversed shape of a forward taper). However, making such a reversedtapered shape is difficult, and further, it causes a problem in that astepwise disconnection of a second electrode 27 which is formed acrossan entire surface of an organic layer 26 and top surface of theinsulation bank 23, as described above, may occur more frequently.Therefore, a stepwise disconnection problem of the second electrode 27will become even severe compared to in the above-described attempt toincrease a height h1 of the insulation bank 23, and thus, it isnecessary to form a second electrode 27 much thicker.

In other words, in the conventional, coated-type organic ELlight-emitting element, it was necessary to make an insulation bank 23liquid repellent, to form an insulation bank 23 in a way to have areversed tapered shape, or to increase a height of an insulation bank23. This caused the problems that, for example, the manufacturingprocess became complex as well as an organic layer 26 was deteriorateddue to an effusion of fluorine or an exposure to the fluorine gasinvolved in a liquid repellent treatment.

On the other hand, in an exemplary embodiment according to the presentapplication, by using an organic material with a smaller degree ofpolymerization, which is neither a polymer compound nor a low moleculeweight compound and has a molecular weight of 300 or more and 5000 orless, preferably about 3000 or less, more preferably 500 or more and1000 or less, in other words, by using an organic material of anoligomer, preferably an oligomer from a dimer to a decamer, as anorganic material to be dissolved in a coating solution, a small liquiddrop of a coating solution having a volume per one drop of about 0.05 pLor more and about 1 pL or less was obtained. This enables to form aninsulation bank 23 to have a smaller height h1 since there is nopossibility that a coating solution 25 a overflows an opening 23 a (see,FIGS. 1A and 1B). A coating solution 25 a will not overflow even if aheight h1 of an insulation bank 23 is, for example, about 1 μm or less.

Further, according to the presently illustrated embodiment, there is noneed to form an insulation bank 23 in a reversed tapered shape. Thus, aninsulation bank 23 may be formed in a forward tapered shape or in ashape in which a sidewall of the insulation bank 23 is substantiallyperpendicular to a surface of the first electrode 22. In other words,according to the presently illustrated embodiment, the insulation bank23 can be formed to have a taper angle θ to the horizontal plane of theinsulation bank 23 (see, FIG. 1A) of 10° or more to 90° or less. In thiscase, the insulation bank 23 can be manufactured more easily compared toan insulation bank 23 with a reversed tapered shape. The insulation bank23 may also be formed in a forward tapered shape with a taper angle θof, for example, about 80° or less. This may further prevent a stepwisedisconnection problem of the second electrode 27. As a result, thestepwise disconnection problem never occurs even when the secondelectrode 27 is formed with a thin thickness, and a light-emittingelement can be formed either as a top emission type light-emittingelement or as a bottom emission type light-emitting element.

Since a small-sized liquid drop was able to be formed as describedabove, the organic layer 26 was formed successfully and precisely evenin a light-emitting area having a much smaller size compared to theconventional size of 70 μm×210 μm, such as a small-sized light-emittingarea of about 10 μm×10 μm, without employing the above-describedattempts that had been made for the conventional, coated-type organic ELlight-emitting element to the insulation bank 23. As a result, even alight-emitting element to be used for a small, high definition displayapparatus such as a smartphone can be formed with a coated-type organiclayer. Further, it was found that a concentration of solute in thecoating solution can be increased to about 10 mass % to 30 mass % byusing an oligomer as an organic material and thus the organic layer canbe formed efficiently even in the small light-emitting area.

A coating solution containing an oligomer according to the presentlyillustrated embodiment is suitably applicable to an area having asimilar size to the conventional, coated-type organic EL light-emittingelement. However, it is particularly effective to a light-emitting areaof 3500 μm² or less, preferably 2500 μm² or less, which has not beenable to be formed from the conventional coated-type organic layer.

Since there is no need to subject a surface of the insulation bank 23 toa liquid repellent treatment, there is no need to form an insulationbank 23 using a fluorine resin containing fluorine or a silicone resin,and a plasma treatment of a surface of the insulation bank 23 by, forexample, CF₄ based gas is also not necessary. Not only that this makes amanufacturing process of an element very simple, but also it can excludean adverse influence that may be caused by an effusion of fluorine fromthe insulation bank 23 or by an exposure to a fluorine-based gas such asCF₄. For example, it may be preferable to use a non-fluorine-based resincontaining no fluorine, such as polyimide-based resin containing nofluorine for an insulation bank 23. As a result, a life prolongation ofthe elements may be achieved. Further, in the presently illustratedembodiment, not only is there no need to conduct a liquid repellenttreatment, but also an insulation bank 23 may be even formed so as tohave a hydrophilic property. A resin having a hydrophilic property asreferred herein involves a resin with no liquid repellent property aswell as a resin to which no specific treatment, i.e. no liquid repellenttreatment, has been conducted, and this may be advantageous because whenan inside of an opening 23 a surrounded by the insulation bank 23 isformed to have a hydrophilic property, a dripped coating solution may beeasily spread up to a peripheral portion of a first electrode 22. As aresult, the first electrode 22 can be covered with a coated layer, up toa peripheral portion of the first electrode 22. This may exclude apossibility of an occurrence of short circuit between the firstelectrode 22 and the second electrode 27 which is formed on an organiclayer 26 after a formation of the organic layer 26 from a coated layer.

For example, a contact angle of a surface of a sidewall of an insulationbank 23 to water may be set to about 15° or more and 60° or less. Bysetting a contact angle of a surface of a sidewall of an insulation bank23 to water to 60° or less, a coating solution being dropped inside anopening 23 a and thinly spreading on a surface of a first electrode 22(a bottom of an opening 23 a) exposed in an opening 23 a (not covered byan insulation bank 23) can wet and spread until the coating solution isin contact with a sidewall of the insulation bank 23, and can form acoated layer with an almost uniform thickness. Further, the coatingsolution that reaches a sidewall of the insulation bank 23 creeps up thesidewall of the insulation bank 23 (see FIG. 1B). Accordingly, in aprocess in which a formed coated layer is dried to form an organiclayer, an aggregation of a solute component onto a central part of afirst electrode 22 within an opening 23 a hardly occurs. After aconcentration of the coated layer reaches to a critical concentration bybeing dried, a height h3 of a contact point between an organic layer 26formed by drying a coated layer and a sidewall of the insulation bank 23(a pinning position) from a surface of a first electrode 22 will begreater than a height h2 of the thinnest part of an organic layer 26from a surface of a first electrode 22, as shown in FIG. 1C.

As described above, when an insulation bank 23 is formed to have aforward tapered shape with a taper angle θ to the horizontal plane of80° or less, a force to keep a coating solution in an opening 23 a maybecome weaker compared to an insulation bank 23 with a taper angle θclose to 90°. Consequently, coating can be performed so as to have afurther uniform layer thickness, and also an area of an organic layer 26having a uniform layer thickness may be extended.

In order to form a surface of an insulation bank 23 to be hydrophilic,for example, the surface of the insulation bank 23 may be subjected to asurface modifying treatment after the formation of the insulation bank23. By conducting a surface modifying treatment, a surface of aninsulation bank 23 may be treated to have a surface roughness ofpreferably 30 nm or less, such as in the range of about 5 nm or more and30 nm or less, in arithmetic average roughness (Ra). It is consideredthat when a surface of an insulation bank 23 has a fine uneven structureon this scale, an insulation bank 23 can show a good hydrophilicity evento a small droplet of a coating solution according to the presentlyillustrated embodiment which has a volume per one drop of about 0.05 pLor more and 1 pL or less. The exemplarily examples of a treatment methodto conduct such a surface modification will be described below, and mayinclude, for example, a rehardening of an insulation bank 23 or anexposure to a dissolving solvent.

The surface of the insulation bank 23 may also be formed to have ahydrophilic property by conducting a surface modifying treatment, suchas UV irradiation treatment, ozone treatment, plasma surface treatment.By conducting a UV irradiation treatment or ozone treatment, chemicalbonding in a surface layer of the insulation bank 23 is cleaved by UV orozone and active oxygen derived from ozone or ozone reacts with amolecule whose chemical bonding is cleaved, and then a polar functionalgroup with a hydrophilic property including, for example, a carboxygroup, hydroxy group, aldehyde group, acrylic group, amide group will beintroduced into the surface layer of the insulation bank 23. Byconducting a plasma surface treatment, the excited active speciesgenerated during plasma discharge act on a surface of the insulationbank 23, and then various hydrophilic functional groups will beintroduced onto a surface of the insulation bank 23 depending on thetype of a plasma source gas. As a plasma source gas, a gas such asargon, nitrogen, hydrogen, ammonia and oxygen may be used and can beselected accordingly. Further, conducting a plasma surface treatmentwill have an advantage when being applied to an insulation bank 23formed using an organic material in that only a surface of theinsulation bank 23 can be mainly modified and the time required for thetreatment will be short. In either case, a hydrophilic surface will beformed through an introduction of the above-described polar functionalgroup onto a surface of the insulation bank 23.

Alternatively, a surface of an insulation bank 23 can be formed to havea hydrophilic property by forming the insulation bank using aparticularly hydrophilic material. The exemplarily examples of aparticularly hydrophilic material may include, but not limited to, aresin such as polyimide or polyamide.

As described above, the inventors found out that by applying a compound,which has a molecular weight of about 300 or more and 5000 or less,preferably about 3000 or less, more preferably about 500 or more and1000 or less and a degree of polymerization similar to the degree theoligomers have, as an organic material for an coated-type organic layer26, a coating solution can drip as a small droplet which has a volumeper one drop of about 0.05 pL or more and 1 pL or less and a nearlyspherical shape to an opening 23 a surrounded by the insulation bank 23which has a hydrophilic surface. Even when the area of a surface of thefirst electrode 22 exposed in the opening 23 a is, for example, 100 μm²or more and 2500 μm² or less, preferably 1200 μm² or less, morepreferably 850 μm² or less, or, 520 μm² or more and 850 μm² or less, inother words, 17 μm×50 μm or less for a high definition panel of a mediumor large size, or 25 μm×25 μm or less for a high definition panel of asmall size, such as a hand-held display apparatus, or a small area wherea length of one side is about 10 μm, a coated-type organic layer can beobtained on that area via an ink-jet process by setting a size of anejecting port of a nozzle of an ink-jet apparatus to about 10 to 20 μmin diameter. Therefore, an organic EL light-emitting element accordingto the presently illustrated embodiment can form a pixel of the organicEL display apparatus, which has a resolution around 500 ppi or a higherpixel density for an apparatus with a size of the smartphone.

However, an upper limit of a size of the area to which an organic layer26 is formed is not limited to the ones described above. When the areais large, a cross-sectional area of an ejecting port of a nozzle will beincreased so that even a large area may be formed in a relatively shorttime. Thus, the above-mentioned length for one side of the pixel havinga rectangular shape is merely an example and a size of the area may beany sizes that correspond to a various pixel shapes for the desireddisplay apparatus. When the shape of an area to be coated is arectangular shape, and if a length of one side of the rectangular shapeis too small (a width of the rectangle is too narrow), it becomesimpossible to apply a liquid drop to the area precisely. Therefore, whena shape of the area to which an organic layer 26 will be formed has arectangular shape, it may be preferable that a short side of therectangle is 10 μm or more. In other words, a squared value of thislower limit of a length of the short side will be a lower limit of asize of a pixel which can be formed by the presently illustratedembodiment. It should be appreciated that a shape of the area to whichan organic layer 26 will be formed, i.e. a shape of a pixel, is notlimited to a rectangular shape or a square shape, and may be a roundshape, elliptic shape, or polygon.

In the presently illustrated embodiment, as described above, even when acoating solution 25 a is coated to a small light-emitting areasurrounded by an insulation bank 23 having a hydrophilic surface, thereis no risk for a coating solution 25 a to overflow an insulation bank23. As a result, an organic layer was formed successfully by a coatingprocess even on an area of the light-emitting area formed with the abovedescribed high definition pattern without an occurrence of color mixingproblem. Since the surface of an insulation bank 23 is hydrophilic, theorganic layer 26 evenly fills a space from a bottom of an opening 23 ato a sidewall of an opening 23 a. As a result, an organic layer 26 withan improved flatness can be obtained, preventing an occurrence of aluminance unevenness or a light emission color unevenness.

An organic layer 26 may include one or more organic layers such as ahole transport layer or an electron transport layer, other than alight-emitting layer. In case where the organic layer 26 is formed witha plurality of layers, a material for each layer should be an organicmaterial containing an oligomer as mentioned above. Further, an organiclayer 26 according to the presently illustrated embodiment may furtherinclude an optional layer between the organic layer 26 and a firstelectrode 22 or a second electrode 27, or between each of the organiclayers when the organic layer 26 is formed by one or more organiclayers. Further, a TFT (not indicated) or a planarization layer (notindicated) and so on may be formed on a substrate 21. It should be notedthat an organic EL light-emitting element shown in FIGS. 1A to 1Caccording to the exemplary embodiment described below is a top emissiontype, however, as described above, it may be formed either for a bottomemission type or a both sides emission type.

An organic EL light-emitting element according to the presentlyillustrated embodiment may be applicable to an illumination apparatus bysealing one or more organic EL light-emitting elements with an envelope(a covering layer) which has at least a translucent front surface, or toa display apparatus by arranging a plurality of light-emitting elementsin matrix form. When applied to an illumination apparatus,light-emitting elements of three colors, red (R), green (G) and blue (B)are enclosed in one envelope, providing a white light emittingillumination apparatus. A white light or a light of any other desirablecolors emitting illumination apparatus may be also formed by covering amonochromatic light emitting element by a fluorescent resin.

When applied to a display apparatus, sub-pixels of three colors, R, Gand B are formed respectively for each pixel (one pixel) arranged inmatrix form, providing a full-color display apparatus. In this case, asize of each sub-pixel is about one-thirds of the size of one pixel, andits area is smaller than the area of one pixel. A material for anorganic layer for each sub-pixel and a planar shape of a sub-pixel couldbe different each other, however, a layered structure formed with, forexample, a first electrode 22, an organic layer 26, a second electrode27 is same, and thus a sub-pixel is herein described as onelight-emitting element (one pixel) without distinguishing a sub-pixelfrom a pixel. An arrangement of the pixels is not particularly limited,and the pixels may be arranged, for example, in a mosaic arrangement, adelta arrangement, a stripe arrangement, a pentile arrangement. In eachpixel, a first electrode 22 of an organic EL light-emitting element isconnected to a driving element, and a predetermined color correspondingto each pixel is emitted by the on-off control of each pixel and variousluminescent colors are realized by mixing different colors.

A substrate 21 may be a support substrate formed with, for example, aglass plate, a polyimide film. In case where the substrate 21 does notneed to be translucent, a metal substrate or a ceramics substrate may beused as well. When applied to a display apparatus, though FIGS. 1A to 1Cdo not illustrate completely, a driving element such as TFT is formed ona position corresponding to an arrangement place for a pixel. Aplanarization layer, which is formed by a material such as acrylic resinor polyimide, may be formed on a driving element for planarization. Amaterial for a planarization layer is not limited to those describedabove, and may be an inorganic material such as SiO₂, SOG, however, anorganic material may be preferable to be applied in order to eliminateirregularities of the surface easily. Further, a first electrode 22 isformed by a combination of a metal layer such as Ag or APC and an ITOfilm at a portion of a surface of the planarization layer whichcorresponds to an area to which an organic EL light-emitting element isformed. An organic layer 26 is coated on the first electrode 22.

An insulation bank 23, which is formed by, for example, a silicon oxide,a silicon nitride, a silicon oxynitride, acrylic resin, polyimide resinor a novolak-type phenol resin, is formed around a first electrode 22which constitutes each pixel, as described in FIGS. 1A to 1C, in orderto divide pixels as well as to prevent a contact between the firstelectrode 22 and the second electrode 27. The insulation bank 23 isformed in such a way that it surrounds at least part of the firstelectrode 22. As shown in FIG. 1A, in the presently illustratedembodiment, the insulation bank 23 is formed in such a way that itcovers a peripheral portion of the first electrode 22 which is formed ina predetermined area. However, an insulation bank 23 may be formed so asto contact with the first electrode 22 without covering the firstelectrode 22 or formed separately from the first electrode 22. In otherwords, an insulation bank 23 may be formed to surround a larger areathan the area to which the first electrode 22 is formed. However, thearea to which the light-emitting element is formed is very small, asdescribed above, it may be preferable to form the insulation bank 23 soas to overlap with a peripheral portion of the first electrode 22.

In either case, it is important to form a layered structure in which thefirst electrode 22 and the second electrode 27, which is formed after aformation of the organic layer 26, are never in contact with one another(inducing a leakage). As described above, it may be preferable that anorganic layer 26 is provided in an area surrounded by an insulation bank23 so as to cover an entire surface of the first electrode 22 which isexposed in an opening 23 a surrounded by the insulation bank 23. Asecond electrode 27 may be formed on the organic layer 26. However, anorganic layer 26 may be formed on the first electrode 22 to have a sizesmaller than the size of the first electrode 22 without covering anentire surface of the first electrode 22, and a second electrode 27 maybe formed on the organic layer 26 to have a size further smaller thanthe size of the organic layer 26.

Among the coated-type organic layers 26, organic materials eachcorrespond to a color from R, G, and B may be used for each oflight-emitting layers. However, a light-emitting layer may be formedusing the same material, and a color filter may be provided on thesurface of the light-emitting layer to obtain a color R, G, or B througha color filter. Further, the organic layer 26 other than alight-emitting layer may include a hole transport layer or an electrontransport layer, or a layered structure thereof. In case where alight-emitting property is considered the most important, it may bepreferable to coat a material suitable for a light-emitting layerseparately for forming a hole transport layer or an electron transportlayer. However, when using a coating process, it is possible to form anorganic EL light-emitting element with a coated-type organic layer 26which includes a fewer number of layers by mixing organic materials eachof which forms respective layers.

For example, in order to form the organic layer 26, as described, forexample, in FIG. 1A, a coating solution 25 a of an organic materialcontaining an oligomer is dropped onto a first electrode 22 surroundedby an insulation bank 23 from a nozzle 31 of an ink-jet apparatus. Anorganic compound having a structure, in which two or more and 10 or lessof monomers, preferably two or more and five or less of monomers,containing a structural unit which contributes to an light-emittingproperty of the material generally applicable to a light-emitting layerof the organic EL light-emitting element are polymerized, may be used asan oligomer. The material generally applicable to a light-emitting layerof the organic EL light-emitting element refers to, for example,materials used as the conventional, dye-based material or polymermaterial. Specifically, an oligomer according to the exemplaryembodiment may be a compound obtained by a polymerization of 2 to 10monomers, which include a structural unit represented by a generalformula (I): —[Y]—, wherein Y includes a skeleton selected from, forexample, a triarylamine skeleton, an oxadiazole skeleton, a triazoleskeleton, a silole skeleton, a styrylarylene skeleton, apyrazoloquinoline skeleton, an oligothiophene skeleton, a ryleneskeleton, a perinone skeleton, a vinyl carobazole skeleton, atetraphenylethylene skeleton, a coumarin skeleton, a rubrene skeleton, aquinacridone skeleton, a squarylium skeleton, a porphyrin skeleton, apyrazoline skeleton.

With a dropping of a coating solution 25 a, a coated layer 25 is formedas described in FIG. 1B. The coated layer 25 spreads into an areasurrounded by an insulation bank 23, which serves as a dam, and remainsin the area, and can stick to an insulation bank 23 without forming aspherical shape since the insulation bank 23 does not have a liquidrepelling property, thereby a surface of the coated layer 25 isplanarized. By drying this, a solvent component in the coating solution25 a is evaporated, providing a thickness being about one-thirtieth ofthe thickness of the coated layer 25, for example, about 10 to 20 nm perone layer (per one material). By conducting this coated-type organiclayer 26 formation process repeatedly with necessary materials, acoated-type organic layer 26 with a pinning position that is provided ina position such that a height of the pinning position from a surface ofthe first electrode 22 is greater than a height of the thinnest part ofan organic layer 26 from a surface of a first electrode 22 is formed asshown in FIG. 1C. In FIG. 1C, the coated-type organic layer 26 isdescried in one layer, however, as described above, in general thecoated-type organic layer 26 will be formed with a plurality of layers.

As described above, in the presently illustrated embodiment, the elementis a top emission type in which a light is emitted from the surface ofthe element which is the opposite to the surface including a substrate21 in FIGs, and thus a second electrode 27 formed on the organic layer26 is formed of a translucent material such as a thin eutectic layercomposed of magnesium and silver. Other materials such as aluminum canbe also used. It should be noted that in case where the element is abottom emission type in which a light is emitted through the substrate21, a material such as ITO, In₃O₄ may be used for a first electrode 22and a metal having a small work function such as Mg, K, Li, Al may beused for a second electrode 27. On the surface of the second electrode27 a protection layer (a covering layer) 28 (see FIG. 1C) may be formed.This covering layer 28 may be replaced with a seal layer (an envelope),which is described below. It may be preferable to form a protectionlayer 28 with a plurality of layers that are formed by the material suchas Si₃N₄, SiO₂, since such a protection layer 28 could provide a finelayer quality. The whole part may be sealed by a seal layer (notindicated) formed by, for example, a glass or a resin film with amoisture-resistant property so as to be formed such that the organiclayer does not absorb water.

As described above, since the organic material for an organic layer 26according to the presently illustrated embodiment is an oligomer, forexample, with a polymerization degree of 2 to 10, having a molecularweight of 300 to 5000, the organic material has a solubility to asolvent sufficient to be applied for a coating solution 25 a for ink-jetprocess which is ejected from a nozzle of ink-jet apparatus to form acoated layer 25 by coating. A concentration of the oligomer in thecoating solution 25 a according to the presently illustrated embodimentmay be adjusted to a concentration which enables to form an organiclayer 26 with a desirable thickness, and it can be, for example, about10 mass % to 30 mass %. Further, since the oligomer has the abovedescribed polymerization degree, only the oligomer having a desirablepolymerization degree can be isolated and purified after the syntheticreaction by a purification method such as a separation by achromatography including a column chromatography and gel permeationchromatography, a reprecipitation, a recrystallization. In the presentlyillustrated embodiment, the oligomer which is highly purified and has nomolecular weight distribution can be used as an organic material for theorganic layer 26, and thus, the color purity and brightness can beenhanced when such an organic material is applied to an organic ELlight-emitting element compared to the element where an organic materialcontaining a polymer compound which is not easily purified and difficultto be obtained as a highly purified compound is used. Also, to use anoligomer of the organic material as an organic material may prevent acrystallization or aggregation of the organic material when beingcoated, and thus, a stability of a layer of the organic layer 26 to beformed may be increased compared to the layer formed from the organicmaterial containing a low molecule weight compound which is, forexample, crystalized easily in general. If a crystallization oraggregation of the organic material occurs in the organic layer, abrightness of the area in which a crystallization or aggregation occursand a layer thickness is relatively increased is relatively decreasedbecause an amount of the current to be injected is reduced compared tothe area in which such a crystallization or aggregation does not occur,possibly causing variation in the distribution of the light emissionintensity within a pixel. Also, there would be a possibility that thelifetime of the element itself may be shortened because of adeterioration occurred in the area having a thin thickness due to aconcentration of current in the area having a relatively thin thickness.The occurrence of this kind of problems can be prevented by using anoligomer of the organic material of the exemplary embodiment of thepresent application for an organic layer 26 of the light-emittingelement. Therefore, an organic EL light-emitting element with a highdefinition having a long lifetime and superior light emission intensitycan be provided by a method for manufacturing a coated-type elementusing a relatively inexpensive printing method.

In one embodiment of the present application, an organic layer 26 of theorganic EL light-emitting element may include one or more organicmaterials which have a superior property such as a hole transportproperty or an electron transport property, in addition to thelight-emitting organic material, as described above. For example, acoating solution 25 a containing a composition formed by mixing anoligomer of an organic material which is a light-emitting material and acompound having a hole transport property or an electron transportproperty may be used for a formation of the organic layer 26. Anoligomer of different kinds of organic materials, for example, anoligomer as a light-emitting material and an oligomer having a holetransport property, may be mixed and used to form an organic layer 26through a coating process. It should be noted that a combination of thematerials is not limited to those described above. This may enable toreduce a number of layers in the organic layer 26 of the organic ELlight-emitting element. Further, this may improve a flatness of theorganic layer 26 and prevent an occurrence of a display unevenness suchas a luminance unevenness or a light emission color unevenness when theorganic layer 26 emits light.

Referring to a flowchart in FIG. 2, an method of manufacturing anorganic EL light-emitting element according to the second embodiment ofthe present application include forming a first electrode 22 on asurface of a substrate 21 (S1), forming an insulation bank 23 tosurround at least part of the first electrode 22 (S2), forming acoated-type organic layer 26 on an area of the first electrode 22surrounded by the insulation bank 23 (S3), and forming a secondelectrode 27 on the organic layer 26 (S4). To a surface of a sidewall ofthe opening 23 a surrounded by the insulation bank 23 is applied amodifying treatment to increase a hydrophilicity, before forming acoated-type organic layer 26 inside the opening 23 a. Further, thisorganic layer 26 is formed by dropping a droplet of a liquid compositioncomprising the above described oligomer of an organic material using anink-jet process. More detailed description will be followed.

When applying the light-emitting element to an organic EL displayapparatus, as described above, a driving TFT, for example, which forms adriving circuit on the substrate 21, is formed with an amorphoussemiconductor, for example, by a usual method using a lithographyprocess, for example. It is planarized by, for example, using apolyimide resin to planarize irregularities of the surface. The firstelectrode 22 is formed in matrix form according to an arrangement ofeach pixels on its surface. This first electrode 22 is also formed byforming the above described material for electrode on the entire surfaceand being subjected to a patterning process (S1).

Subsequently, the insulation bank 23 is formed (S2). This insulationbank 23 may be formed by an inorganic material such as a silicon oxide,a silicon nitride, a silicon oxynitride, or, if a thicker layer isrequired, it may be formed in a short time by using a resin materialsuch as acrylic resin, polyimide resin or novolak-type phenol resin. Aninsulation bank 23, which includes an opening 23 a that exposes at leastpart of the first electrode inside thereof as illustrated in FIG. 1A, isformed by (i) forming an insulation layer on the entire surface with athickness of, for example, about 1 μm, which should provide a sufficientheight for an insulation bank 23, and (ii) being subjected to apattering process using a photolithography technique. In this case, aninsulation bank 23 may be formed in a forward tapered shape as describedabove, or in a shape in which a sidewall of the insulation bank 23 issubstantially perpendicular to the first electrode 22. A surfacemodifying treatment such as ashing or plasma treatment may be conductedto a surface of the first electrode 22 exposed in the opening 23 a afterthe formation of the insulation bank 23. This makes it possible, forexample, to provide a hydrophilic property to a surface of the firstelectrode 22, to remove (be cleaning) an organic substance adhered to asurface of the first electrode 22, or to adjust a work function near thesurface of the first electrode 22. Further, this can make an adhesivestrength between an organic layer 26 to be formed on a first electrode22 and a first electrode 22 stronger.

Further, a surface modifying treatment may be conducted to a surface ofa sidewall of the opening 23 a surrounded by of the insulation bank 23.For example, this kind of surface modifying treatment can be conductedby rehardening a surface of an insulation bank 23 after the insulationbank 23 was formed in a desirable shape. For example, after aninsulation bank 23 is cured at a curing temperature of the resinmaterial, the insulation bank is baked at a temperature higher than thecuring temperature, for example, the temperature about 15° C. to 30° C.higher than the curing temperature, for about 5 min to 30 min, forexample. This temporarily softens the surface of the insulation bank 23,and then the surface of the insulation bank 23 is rehardened. This canimprove a flatness of the surface of the insulation bank 23.Alternatively, a modifying treatment may be conducted, for example, byexposing an insulation bank 23 formed in a desired shape to anatmosphere of the solvent that can dissolve the resin material for aninsulation bank 23 for about 5 min to 30 min. These surface modifyingtreatments enable to modify a surface of the insulation bank 23 into thesurface having an arithmetic average roughness of about 5 nm or more and30 nm or less. This can improve a hydrophilicity of a surface of theinsulation bank 23.

A surface modifying treatment, such as UV irradiation treatment, ozonetreatment, plasma surface treatment may be conducted to the surface of asidewall of the opening 23 a surrounded by the insulation bank 23. Thiskind of modifying treatments increase a surface free energy of thesurface of the insulation bank 23, resulting in an improvement of thehydrophilicity of the insulation bank 23.

And then, a coating solution 25 a of the above mentioned organicmaterial is ejected from a nozzle 31 by an ink-jet process, asillustrated in FIG. 1A. The ejection of the coating solution 25 a isconducted by aligning the nozzle 31 to the first electrode 22 exposed inthe opening 23 a surrounded by the insulation bank 23. As illustrated inFIG. 1B, an ejected coating solution 25 a forms a coated layer 25 in theopening 23 a surrounded by the insulation bank 23 (S3).

In particular, as illustrated in FIG. 1A, a coating solution 25 a of anorganic material containing the oligomer according to the embodiment ofthe present application is ejected from a nozzle 31 of the ink-jetapparatus and drips on an area of the first electrode 22 surrounded bythe insulation bank 23. A coating solution 25 a may be a liquidcomposition containing at least an oligomer according to the embodimentof the present application and a solvent. Any solvents capable ofdissolving an organic material containing an oligomer according to theembodiment of the present application may be used, and preferably anorganic solvent may be used. Examples of the organic solvent is notparticularly limited, however, when a low-boiling point solvent is usedas a solvent, this would cause a clogging in the nozzle of ink-jetapparatus, or, a thickness unevenness would be occurred since drying ofa coating solution 25 a may begin right after being ejected from anozzle 31 and a solute may be precipitated. Therefore, a low-boilingpoint solvent may be preferably used in combination with a solventhaving a higher boiling point. For example, as the solvent, a chlorinebased solvent, ether based solvent, aromatic hydrocarbon based solvent,aliphatic hydrocarbon based solvent, ketone based solvent, ester basedsolvent, alcohol based solvent, amide based solvent, and a mixed solventthereof are exemplified. Among them, a mixed solvent containingcyclohexylbenzene, xylene or anisole, or one or more of those may bepreferable in terms of, for example, an evenness of a formed layer andviscosity property of a coating solution 25 a, but a solvent is notlimited to those. A coating solution 25 a may be prepared to have aviscosity at 25° C. of about 0.6×10⁻³ Pa·s or more and about 3×10⁻³ Pa·sor less, preferably about 1×10⁻³ Pa·s or less. With a viscosity of thisrange, a coating solution 25 a can be ejected from an ink-jet head as adroplet having a substantially constant particle diameter, and a steadyejection from the ink-jet apparatus can be realized even when using anapparatus provided with multiple nozzles.

Subsequently, a eutectic layer composed of magnesium and silver, forexample, is formed by, for example, a vapor-deposition on the entiresurface to form a second electrode 27 on the organic layer 26 (S4). Inthe organic EL light-emitting element according to the presentlyillustrated embodiment, the second electrode 27 serves as a cathode. Anexample of the material which constitutes a second electrode 27 is asdescribed above, and the second electrode 27 is formed of a thin metallayer to have a thickness of about 5 nm or more and 30 nm or less. Thesecond electrode 27 is formed on the entire surface including the topsurface of the insulation bank 23, since it is formed as a commonelectrode for each pixel.

Next, a protection layer 28 which serves as a seal layer to prevent apenetration of water and/or oxygen from the outside is formed on thesecond electrode 27. This protection layer 28 may be an inorganic layerformed of, for example, Si₃N₄ or SiO₂, which has no hygroscopic propertyand may be formed by bonding to a substrate 21 (not indicated) in such away to entirely cover the second electrode 27 and organic layer 26 andso on. Consequently, the organic EL light-emitting element of theembodiment of the present application is completed (see FIG. 1C). Thismethod is described herein as merely an exemplary example, and a methodof manufacturing an organic EL light-emitting element of the embodimentof this application may further include optional steps between eachstep. For example, when a coating solution 25 a is dropped multipletimes on different positions in an area surrounded by the insulationbank 23 as described above, a planarization process may be conducted toplanarize a coating solution 25 a dripped in the area before the dryingprocess of the coated layer 25.

As described above, by using an organic material containing an oligomerof the organic material as an organic material for the organic layer 26of the organic EL light-emitting element and by forming a surface of theinsulation bank 23 to have a hydrophilic property, a coated-type organiclayer 26 can be provided excellently on an small-sized area on theelectrode. As a result, a display unevenness such as a thicknessunevenness can be reduced, and an organic EL light-emitting element witha high definition pattern having a superior light-emission property canbe obtained at a low cost.

(Summary)

(1) An organic electroluminescent light-emitting element according tothe first embodiment of the present application includes a substrate, afirst electrode provided on a surface of the substrate, an insulationbank formed to surround at least part of the first electrode, an organiclayer formed on the first electrode surrounded by the insulation bank,and a second electrode formed on the organic layer, wherein theinsulation bank has a forward tapered shape or a sidewall of theinsulation bank is formed such as to be substantially perpendicular tothe first electrode, and a surface of the insulation bank is formed tohave a hydrophilic property, and the organic layer is a coated-typeorganic layer comprising an oligomer of an organic material.

According to the organic EL light-emitting element of the exemplaryembodiment of the present application, a volume per one drop of a liquiddrop of a liquid composition to be ejected form a nozzle of the ink-jetapparatus to form a coated layer can be small since the organic materialto form a coated-type organic layer contains an oligomer, and thus,there is no possibility that a liquid composition overflows theinsulation bank and spreads to the electrodes of neighboring pixels.This enables a high definition pattern formation of pixels by coatingprocess. Further, since the surface of the insulation bank is formed tohave a hydrophilic property, a dripped coating solution ejected to forma coated layer may be easily spread onto a surface of the insulationbank, enabling to form the organic layer which evenly fills up to asidewall of an opening surrounded by the insulation bank. The organiclayer with an excellent flatness can be formed on the first electrode.

(2) It may be preferable that an angle of the sidewall of the insulationbank to the first electrode is 10° or more and 90° or less. This makesit possible to prevent a stepwise disconnection problem of the secondelectrode which is formed across an entire surface of an organic layerand top surface of the insulation bank from occurring.

(3) It may be preferable that the surface of the insulation bank is amodified surface having an arithmetic average roughness of 5 nm or moreand 30 nm or less. By modifying a surface in this way, a hydrophilicsurface can be obtained.

(4) It may be preferable that a contact angle of a surface of theinsulation bank to water is 15° or more and 60° or less. With a surfaceof the insulation bank having a water contact angle in this range, anexcellent hydrophilicity can be obtained.

(5) It may be preferable that a pinning position of the organic layer isprovided in a position such that a height of the pinning position isgreater than a height of a thinnest part of the organic layer, thepinning position being a contact point between the organic layer and thesidewall of the insulation bank. This makes it possible to form anorganic layer with an improved flatness and prevent an occurrence of,for example, a luminance unevenness.

(6) Further, a method of manufacturing an organic EL light-emittingelement of the second embodiment of the present application includesforming a first electrode on a surface of a substrate, forming aninsulation bank to surround at least part of the first electrode,forming a coated-type organic layer on an area of the first electrodesurrounded by the insulation bank, and forming a second electrode on theorganic layer, wherein the method comprises conducting a modifyingtreatment to increase a hydrophilicity to a surface of a sidewall of anopening surrounded by the insulation bank before forming the organiclayer, and a step for forming the organic layer is conducted by applyinga droplet of a liquid composition comprising an oligomer of an organicmaterial using an ink-jet process.

According to the method of manufacturing an organic EL light-emittingelement of the second embodiment of the present application, even when asize of pixel is small, an organic EL light-emitting element with anorganic layer having an excellent flatness can be formed with a highdefinition pattern on a pixel electrode by a coating process. Therefore,a small-sized, high definition organic EL light-emitting element can bemanufactured easily and inexpensively.

(7) It may be preferable that the modifying treatment is conducted bymodifying an arithmetic average roughness of a surface of the insulationbank through a rehardening of the surface of the insulation bank or anexposure to a dissolving solvent, since this enables a formation of aninsulation bank having an improved hydrophilicity.

(8) It may be preferable that the modifying treatment is conducted byintroducing a polar functional group onto a surface of the insulationbank by a plasma irradiation, a UV irradiation, or an ozone treatment,since this enables a formation of an insulation bank having an improvedhydrophilicity.

DESCRIPTION OF REFERENCE NUMERALS

-   21 substrate-   22 first electrode-   23 insulation bank-   23 a opening-   25 coated layer-   25 a coating solution-   26 organic layer-   27 second electrode-   28 protection layer-   31 nozzle

1. A top emission type organic electroluminescent light-emitting elementcomprising: a substrate, a first electrode provided on a surface of thesubstrate, an insulation bank formed to surround at least part of thefirst electrode, one or more organic layers formed on the firstelectrode surrounded by the insulation bank, and a second electrodehaving translucency formed on the one or more organic layers, whereinthe insulation bank has a forward tapered shape or a sidewall of theinsulation bank is formed such as to be substantially perpendicular tothe first electrode, and a surface of the insulation bank is formed tohave a hydrophilic property, and a contact angle of the surface of theinsulation bank to water is 15° or more and 60° or less, each of the oneor more organic layers is a coated-type organic layer formed of anoligomer having a molecular weight of 300 or more and 5000 or less of anorganic material, and the one or more organic layers comprise alight-emitting layer, a thickness of the second electrode is 5 nm ormore and 30 nm or less, and light is taken out from a surface of the topemission type organic electroluminescent light-emitting element, thesurface including the second electrode.
 2. The top emission type organicelectroluminescent light-emitting element of claim 1, wherein theinsulation bank has the forward tapered shape and an angle of thesidewall of the insulation bank to the first electrode is 10° or moreand 80° or less.
 3. The top emission type organic electroluminescentlight-emitting element of claim 1, wherein the surface of the insulationbank is a modified surface having an arithmetic average roughness of 5nm or more and 30 nm or less.
 4. The top emission type organicelectroluminescent light-emitting element of claim 1, wherein a pinningposition of the one or more organic layers is provided in a positionsuch that a height of the pinning position from a surface of the firstelectrode is greater than a height of a thinnest part of the one or moreorganic layers from a surface of the first electrode, the pinningposition being a contact point between the one or more organic layersand the sidewall of the insulation bank.
 5. The top emission typeorganic electroluminescent light-emitting element of claim 1, wherein anarea of the first electrode surrounded by the insulation bank is 100 μm2or more and 850 μm2 or less.
 6. A method of manufacturing a top emissiontype organic electroluminescent light-emitting element comprising:forming a first electrode on a surface of a substrate, forming aninsulation bank to surround at least part of the first electrode,forming one or more organic layers comprising a light-emitting layer onan area of the first electrode surrounded by the insulation bank, eachof the one or more organic layers being formed of an oligomer having amolecular weight of 300 or more and 5000 or less of an organic material,and each of the one or more organic layers being formed as a coated-typeorganic layer, and forming a second electrode having translucency on theone or more organic layers, wherein the method comprises conducting amodifying treatment to a surface of a sidewall of an opening surroundedby the insulation bank so as to have a contact angle of the surface ofthe sidewall of the opening surrounded by the insulation bank to waterof 15° or more and 60° or less before forming the one or more organiclayers, the second electrode is formed to have a thickness of 5 nm ormore and 30 nm or less, each of the one or more organic layers is formedby supplying a droplet with a volume per one drop of 0.05 pL or more and1 pL or less of a liquid composition comprising the oligomer of theorganic material for the one or more organic layers using an ink-jetprocess, and the top emission type organic electroluminescentlight-emitting element is formed such that light is taken out from asurface of the top emission type organic electroluminescentlight-emitting element, the surface of the top emission type organicelectroluminescent light-emitting element including the secondelectrode.
 7. The method of manufacturing a top emission type organicelectroluminescent light-emitting element of claim 6, wherein themodifying treatment is conducted by modifying an arithmetic averageroughness of a surface of the insulation bank through a rehardening ofthe surface of the insulation bank or an exposure to a dissolvingsolvent.
 8. The method of manufacturing a top emission type organicelectroluminescent light-emitting element of claim 6, wherein themodifying treatment is conducted by introducing a polar functional grouponto a surface of the insulation bank by a plasma irradiation, a UVirradiation, or an ozone treatment.
 9. The method of manufacturing a topemission type organic electroluminescent light-emitting element of claim6, wherein the insulation bank is formed such that the area of the firstelectrode surrounded by the insulation bank is 100 μm2 or more and 850μm2 or less.